GRB 251016B
GCN Circular 42332
Subject
Fermi GRB 251016B: Global MASTER-Net observations report
Date
2025-10-17T20:01:03Z (3 days ago)
From
Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>
Via
email
V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko,
G.Antipov, A.Sankovich, Yu.Tselik, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU),
O.Gress, N.Budnev (ISU),
C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA),
A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),
A.Sosnovskij (CrAO),
A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity),
D.Buckley (SAAO),
R.Rebolo (The Instituto de Astrofisica de Canarias),
L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez,
A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory)
MASTER-Kislovodsk robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) started inspect of the Fermi GRB 251016B ( Fermi GBM team, GCN 42316) errorbox 64428 sec after notice time and 64463 sec after trigger time at 2025-10-17 17:53:24 UT, with upper limit up to 18.4 mag. The observations began at zenith distance = 75 deg. The sun altitude is -38.0 deg.
The galactic latitude b = 57 deg., longitude l = 131 deg.
Real time updated cover map and OT discovered available here:
https://master.sai.msu.ru/site/master2/observ.php?id=3016439
We obtain a following upper limits.
Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________
64493 | 2025-10-17 17:53:24 | MASTER-Kislovodsk | (12h 10m 29.71s , +59d 47m 44.4s) | C | 60 | 17.9 |
64493 | 2025-10-17 17:53:24 | MASTER-Kislovodsk | (12h 02m 34.87s , +60d 07m 45.3s) | C | 60 | 18.2 |
64573 | 2025-10-17 17:54:44 | MASTER-Kislovodsk | (11h 59m 57.83s , +57d 53m 49.9s) | C | 60 | 17.7 |
64653 | 2025-10-17 17:56:03 | MASTER-Kislovodsk | (12h 28m 38.77s , +57d 56m 06.7s) | C | 60 | 17.7 |
64653 | 2025-10-17 17:56:03 | MASTER-Kislovodsk | (12h 21m 10.62s , +58d 16m 11.0s) | C | 60 | 17.9 |
64733 | 2025-10-17 17:57:23 | MASTER-Kislovodsk | (12h 23m 18.88s , +61d 41m 55.2s) | C | 60 | 17.6 |
64733 | 2025-10-17 17:57:23 | MASTER-Kislovodsk | (12h 14m 53.21s , +62d 01m 54.8s) | C | 60 | 18.2 |
64976 | 2025-10-17 18:01:26 | MASTER-Kislovodsk | (12h 32m 54.86s , +60d 10m 17.7s) | C | 60 | 18.2 |
65135 | 2025-10-17 18:04:06 | MASTER-Kislovodsk | (12h 10m 31.27s , +59d 47m 15.5s) | C | 60 | 17.9 |
65135 | 2025-10-17 18:04:06 | MASTER-Kislovodsk | (12h 02m 38.29s , +60d 07m 24.6s) | C | 60 | 18.4 |
65216 | 2025-10-17 18:05:26 | MASTER-Kislovodsk | (12h 00m 00.77s , +57d 53m 08.9s) | C | 60 | 17.6 |
65296 | 2025-10-17 18:06:46 | MASTER-Kislovodsk | (12h 28m 41.30s , +57d 55m 38.0s) | C | 60 | 17.6 |
65296 | 2025-10-17 18:06:46 | MASTER-Kislovodsk | (12h 21m 14.36s , +58d 15m 48.0s) | C | 60 | 18.0 |
65781 | 2025-10-17 18:14:51 | MASTER-Kislovodsk | (12h 23m 20.47s , +61d 42m 21.0s) | C | 60 | 17.6 |
65781 | 2025-10-17 18:14:52 | MASTER-Kislovodsk | (12h 14m 56.78s , +62d 02m 32.5s) | C | 60 | 18.1 |
66021 | 2025-10-17 18:18:52 | MASTER-Kislovodsk | (12h 33m 02.17s , +60d 07m 57.4s) | C | 60 | 18.1 |
66181 | 2025-10-17 18:21:31 | MASTER-Kislovodsk | (12h 10m 40.13s , +59d 48m 37.0s) | C | 60 | 17.9 |
66181 | 2025-10-17 18:21:31 | MASTER-Kislovodsk | (12h 02m 49.68s , +60d 08m 56.5s) | C | 60 | 18.3 |
66261 | 2025-10-17 18:22:51 | MASTER-Kislovodsk | (12h 00m 02.22s , +57d 53m 04.0s) | C | 60 | 17.6 |
66341 | 2025-10-17 18:24:11 | MASTER-Kislovodsk | (12h 28m 46.58s , +57d 54m 54.8s) | C | 60 | 17.6 |
66341 | 2025-10-17 18:24:12 | MASTER-Kislovodsk | (12h 21m 22.73s , +58d 15m 14.6s) | C | 60 | 17.9 |
66632 | 2025-10-17 18:29:02 | MASTER-Kislovodsk | (12h 23m 25.23s , +61d 42m 58.9s) | C | 60 | 17.7 |
66632 | 2025-10-17 18:29:02 | MASTER-Kislovodsk | (12h 15m 03.72s , +62d 03m 15.8s) | C | 60 | 18.1 |
67078 | 2025-10-17 18:36:28 | MASTER-Kislovodsk | (12h 33m 12.10s , +60d 09m 22.3s) | C | 60 | 18.1 |
67237 | 2025-10-17 18:39:07 | MASTER-Kislovodsk | (12h 10m 48.06s , +59d 48m 19.7s) | C | 60 | 17.9 |
67237 | 2025-10-17 18:39:08 | MASTER-Kislovodsk | (12h 02m 58.20s , +60d 08m 43.5s) | C | 60 | 18.1 |
67317 | 2025-10-17 18:40:27 | MASTER-Kislovodsk | (12h 00m 05.23s , +57d 53m 23.6s) | C | 60 | 17.6 |
67397 | 2025-10-17 18:41:47 | MASTER-Kislovodsk | (12h 28m 47.12s , +57d 54m 50.5s) | C | 60 | 17.6 |
67397 | 2025-10-17 18:41:47 | MASTER-Kislovodsk | (12h 21m 23.71s , +58d 15m 15.1s) | C | 60 | 18.0 |
67687 | 2025-10-17 18:46:37 | MASTER-Kislovodsk | (12h 23m 27.68s , +61d 40m 36.8s) | C | 60 | 17.6 |
67687 | 2025-10-17 18:46:37 | MASTER-Kislovodsk | (12h 15m 10.60s , +62d 00m 56.4s) | C | 60 | 18.1 |
67926 | 2025-10-17 18:50:37 | MASTER-Kislovodsk | (12h 33m 18.29s , +60d 07m 34.3s) | C | 60 | 18.1 |
68293 | 2025-10-17 18:56:43 | MASTER-Kislovodsk | (12h 10m 54.87s , +59d 48m 17.3s) | C | 60 | 17.9 |
68293 | 2025-10-17 18:56:43 | MASTER-Kislovodsk | (12h 02m 59.73s , +60d 08m 46.1s) | C | 60 | 18.2 |
68373 | 2025-10-17 18:58:03 | MASTER-Kislovodsk | (12h 00m 24.20s , +57d 53m 11.7s) | C | 60 | 17.6 |
68452 | 2025-10-17 18:59:23 | MASTER-Kislovodsk | (12h 28m 56.85s , +57d 52m 31.8s) | C | 60 | 17.6 |
68453 | 2025-10-17 18:59:23 | MASTER-Kislovodsk | (12h 21m 29.31s , +58d 13m 01.5s) | C | 60 | 17.9 |
68753 | 2025-10-17 19:04:23 | MASTER-Kislovodsk | (12h 23m 37.61s , +61d 41m 55.7s) | C | 60 | 17.6 |
68754 | 2025-10-17 19:04:24 | MASTER-Kislovodsk | (12h 15m 21.05s , +62d 02m 17.0s) | C | 60 | 18.1 |
68994 | 2025-10-17 19:08:25 | MASTER-Kislovodsk | (12h 33m 21.64s , +60d 08m 01.0s) | C | 60 | 18.1 |
69157 | 2025-10-17 19:11:08 | MASTER-Kislovodsk | (12h 10m 49.35s , +59d 47m 14.2s) | C | 60 | 17.6 |
69157 | 2025-10-17 19:11:08 | MASTER-Kislovodsk | (12h 03m 11.06s , +60d 07m 42.8s) | C | 60 | 18.2 |
69445 | 2025-10-17 19:15:56 | MASTER-Kislovodsk | (12h 00m 15.93s , +57d 52m 23.4s) | C | 60 | 17.6 |
69525 | 2025-10-17 19:17:15 | MASTER-Kislovodsk | (12h 28m 54.84s , +57d 54m 20.9s) | C | 60 | 17.5 |
69525 | 2025-10-17 19:17:15 | MASTER-Kislovodsk | (12h 21m 39.39s , +58d 14m 53.4s) | C | 60 | 18.1 |
69815 | 2025-10-17 19:22:05 | MASTER-Kislovodsk | (12h 23m 48.31s , +61d 42m 05.7s) | C | 60 | 17.6 |
69815 | 2025-10-17 19:22:05 | MASTER-Kislovodsk | (12h 15m 32.13s , +62d 02m 32.5s) | C | 60 | 18.0 |
69975 | 2025-10-17 19:24:45 | MASTER-Kislovodsk | (11h 58m 36.13s , +61d 27m 27.6s) | C | 60 | 17.9 |
70055 | 2025-10-17 19:26:05 | MASTER-Kislovodsk | (12h 33m 35.77s , +60d 07m 51.8s) | C | 60 | 17.9 |
Filter C is a clear (unfiltred) band.
The observation and reduction will continue.
The message may be cited.
GCN Circular 42324
Subject
GRB 251016B: AstroSat CZTI detection
Date
2025-10-17T10:34:55Z (3 days ago)
From
Anuraag Arya at IIT Bombay <aryaanuraag910@gmail.com>
Via
Web form
Harsha K. H. (IUCAA), M. Tembhurnikar (IUCAA), S. Salunke (IUCAA), A. Arya (IITB), U. Pathak (IITB), A. Goyal (IITB), G. Waratkar (Caltech/IITB), A. Vibhute (IUCAA), V. Bhalerao (IITB), D. Bhattacharya (Ashoka University/IUCAA), A. R. Rao (IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration:
Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al., 2021, JApA, 42, 73) showed the detection of a bright,long GRB 251016B which was also detected by Fermi GBM (Fermi GBM Team, GCN Circ. 42316).
The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve peaks at 2025-10-16 23:59:03.85 UTC. The measured peak count rate associated with the burst is 1394 (+217, -85) counts/s above the background in the combined data of three quadrants (out of four), with a total of 4295 (+210, -209) counts. The local mean background count rate was 214 (+6, -8) counts/s. Using cumulative rates, we measure a T90 of 5.4 (+0.8, -0.5) s. In the preliminary analysis, we find 498 Compton events associated with this event.
The source was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve peaks at 2025-10-16 23:59:02.60 UTC. The measured peak count rate associated with the burst is 1972 (+90, -100) counts/s above the background in the combined data of all quadrants, with a total of 6747 (+290, -334) counts. The local mean background count rate was 1255 (+6, -6) counts/s. We measure a T90 of 5.2 (+1.8, -0.7) s from the cumulative Veto light curve.
CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, URSC, IUCAA, SAC, and PRL. The Indian Space Research Organisation funded, managed, and facilitated the project.
CZTI GRB detections are reported regularly on the payload site at:
http://astrosat.iucaa.in/czti/?q=grb
GCN Circular 42320
Subject
GRB 251016B: CALET Gamma-Ray Burst Monitor detection
Date
2025-10-17T07:01:32Z (3 days ago)
From
Yuta Kawakubo at Aoyama Gakuin University <kawakubo@phys.aoyama.ac.jp>
Via
Web form
K. Yamaoka (Nagoya U), A. Yoshida, T. Sakamoto, S. Sugita, Y. Kawakubo (AGU),
S. Nakahira (JAXA), Y. Asaoka (ICRR), S. Torii, Y. Akaike, K. Kobayashi (Waseda U),
Y. Shimizu, T. Tamura (Kanagawa U), N. Cannady (GSFC/UMBC), M. L. Cherry (LSU),
S. Ricciarini (U of Florence), P. S. Marrocchesi (U of Siena),
and the CALET collaboration:
The long GRB 251016B (Fermi GBM Final Real-time Localization: Fermi GBM team,
GCN Circ. 42316) triggered the CALET Gamma-ray Burst Monitor (CGBM) at
23:58:57.45 UTC on 16 October 2025
(https://cgbm.calet.jp/cgbm_trigger/flight/1444693868/index.html).
The burst signal was seen by all CGBM detectors.
The burst light curve shows a single pulse that starts
at T+3.1 sec, peaks at T+5.6 sec, and ends at T+12.6 sec.
The T90 and T50 durations measured by the SGM data are 5.9 +/- 0.5 sec
and 2.0 +/- 0.1 sec (40-1000 keV), respectively.
The ground-processed light curve is available at
https://cgbm.calet.jp/cgbm_trigger/ground/1444693868/
The CALET data used in this analysis are provided by
the Waseda CALET Operation Center located at Waseda University.
GCN Circular 42316
Subject
GRB 251016B: Fermi GBM Final Real-time Localization
Date
2025-10-17T00:10:30Z (4 days ago)
From
Fermi GBM Team at MSFC/Fermi-GBM <do_not_reply@GIOC.nsstc.nasa.gov>
Via
email
The Fermi GBM team reports the detection of a likely LONG GRB
At 23:59:00 UT on 16 Oct 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251016B (trigger 782351945.722452 / 251016999).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 183.6, Dec = 59.6 (J2000 degrees, equivalent to J2000 12h 14m, 59d 36'), with a statistical uncertainty of 1.0 degrees.
The angle from the Fermi LAT boresight is 46.0 degrees.
The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251016999/quicklook/glg_skymap_all_bn251016999.png
The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251016999/quicklook/glg_healpix_all_bn251016999.fit
The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251016999/quicklook/glg_lc_medres34_bn251016999.gif